322 HETEROMORPHY. 



are opposite in each verticil and crossed in the two 

 successive ones. The stem is four-angled, each angle 

 having a nerve. Each of these nerves, springing from 

 the origin of a branch in one whorl, terminates in the 

 interval which separates the point of origin of the two 

 branches in the whorl next above it. In the deformed 

 stem one of the nerves corresponds to the insertion of a 

 branch, its neighbour is in the adjoining vacant space ; 

 hence it results that four nerves correspond to two 

 branches and to two consecutive interspaces, and hence 

 the analogy between a single normal internode provided 

 with its two branches and its four nerves. What con- . 

 firms this inference is that the nerve, which begins 

 at the point of origin of a branch, after making one 

 spiral turn round the stem, terminates in the interval 

 that separates the two following branches, just as in a 

 branch of the normal stem it ends in the upper whorl 

 between the two next branches. The torsion, then, in 

 this Galium caused the separation of the two opposite 

 branches of the same verticil, and placed them one 

 above another, and this being reproduced in all the 

 whorls, all the branches come to be arranged on the 

 same longitudinal line. The leaves are susceptible of 

 the same explanation ; they are inserted in groups of 

 three or four in one arc round the origin of each 

 branch. In the malformation each series or group of 

 four leaves, with its central branch, is equivalent to 

 half a whorl of the natural plant with its axillary 

 branch. In other words, the malformation consists in 

 a torsion of the stem, which separates each whorl 

 into two distinct halves ; these half- whorls, with their 

 axillary branches, are placed on a single longitudinal 

 series one above another. This case is quoted at some 

 length, as it is an admirable example of a very common 

 form of malformation in these plants. 



In some parts of Holland where madder is culti- 

 vated a similar deformation is particularly frequent. 

 The leaves, however, are not always grouped in the 

 way in which they were described by M. Duchartre, 



